Process for ether purification



Sept. 3, 1957 DISTILLATION COLUMN E. T.DELAUNE ETAL 2,805,262

PROCESS FOR EITHER PURIFICATION Filed March 10, 1955 5 I m 2; L :F 5 r 2pf 2 f e: a:

ELAINE T. UELAUNE SAMUEL W. WILSON INVENTURS SAMUEL J. MAYEUX, JR.

BY Walk/,1. ATTORNEY United Sttes Patent C PROCESS FOR ETHERPURIFICATION Elaine T. Delaune, Samuel W. Wilson, and Samuel J. Mayeux,Jr., Baton Rouge, La., assignors to Essa Research and EngineeringCompany, a corporation of Delaware The present invention relates to amethod of purifying a crude volatile aliphatic ether such as a crudeethyl or isopropyl ether prepared by the reaction of an olefin withsulfuric acid. More particularly, the present invention relates to aprocess for upgrading an aliphatic ether by removing objectionable odorstherefrom and producing a high quality product suitable for industrial,reagent and pharmaceutical purposes.

High grades of chemically pure, anhydrous, and reagent grade ethylethers have been manufactured in the past on a small scale for use aslaboratory agents or special solvents. To obtain the required highdegree of purity required for these grades, it was generally considerednecessary that the ether be produced by a re action of rather pureethanol and sulfuric acid followed by lengthy steps of washing,neutralizing, and redistilling. Involved purification treatments wererequired for removal of impurities such as aldehydes, free acid,peroxides, odor and color forming substances and the like.

In the development of alcohol syntheses from olefins on a large scale,large amounts of crude ether by-products have become available, leadingto the necessity of refining the crude ethers on a large industrialscale in order to obtain commercially saleable and high grade etherproducts.

In particular, it is necessary to remove foreign odors for these makeeven otherwise high quality ethers unsuitable for many purposes, such asin pharmaceuticals and the like. These odor-imparting constituents arepresent in apparently very small concentrations, but are very difficultto remove by treating techniques generally employed in improving theodor of organic materials. Thus, percolation of finished ether throughvarious solid absorben-ts such as charcoal, silica gel, sand, or aluminagave no significant improvement in the odor. Even with exceptionallyhigh fractionation efficiency in the final distillation step, completeodor removal was not realized. A similar result was obtained byemployment of treating agents such as H2804, water, KOH, KMnO4 and thelike. It is thus evident that the ether odor problem is an important anddifiicult one.

An object of the present invention is to provide a method ofpurification that will produce a finished ether product of high puritysubstantially free of foreign odors.

A further object of the present invention is to provide an economicalether purification treatment which is adapted for use in combinationwith a large scale distillation refining on a continuous basis withavoidance of timeand material-consuming steps.

Other objects and advantages of this invention will be made apparent inthe following description.

In accordance with the present invention, diethyl ether produced by thesulfation of ethylene is improved with respect to odor by maintaining asmall amount of ethyl alcohol in the ether, or by adding a small amountof ethyl alcohol to the ether, to maintain an alcohol content of notless than 0.5 volume percent, and preferably 1%, and preferably no morethan about 10%, and contacting this solution with a solution of sodiumplumbite, and thereafter distilling the treated ether. The sodiumplumbite treated ether after distillation is vastly improved as to odoras compared to the same ether not so treated but distilled, or treatedby reagents set forth :above, such as H2804, NaHSO3, etc.

A satisfactory procedure by which the invention is practiced isdescribed in reference to the accompanying drawing, which'is a schematicflow plan of a continuous ether refining system for illustratingpreferred embodiments of the invention.

Turning now to the figure, crude ethanol which is made by reactingethylene with sulfuric acid, followed by hydrolysis and stripping andwater dilution to eflect separation of high boiling water-insolublecontaminants or in a manner known to the art, is fed via line 1 to theether 01 heads column 2. In this distillation column, conditions aremaintained such that ether, alcohol and water are taken overhead. Somewater-insoluble impurities may also be removed in the over-. headstream. Crude ether containing from 0.5-40% (vol.) of alcohol is takenoff overhead via line 3 and condenser 4 and is returned in part asreflux to column 2 via line 5. Tower 2 may be operated to take overheadmore than 1-2% alcohol; in such case a portion of the overhead is sentto ether washer 7 via line 6. Wa-. ter is added to ether washer 7through line 8, and a temperature of 85 F. and a pressure sufficient tokeep the ether in the liquid phase are maintained. The washed ethercontaining a small amount of alcohol, gen: erally less than 1% byvolume, is taken overhead or as the top phase and is sent via line 9 tothe ether purification unit of the invention. This crude washed othermay contain as impurities varying amounts of high boiling materials, lowboiling impurities, sulfurcompounds, organic acids, and the like.

The ether-free bottoms from column 2 are passed via line 10 torectifying column 25 for alcohol recovery purification, andconcentration. Side streams may be withdrawn from column 25 via line 11and passed to ether washer 7 via line 6, where high boilers areextracted 'by the ether as water-insoluble impurities. All or a portionof the side streams may also be returned to heads column 2 via lines 11and 12.

If the heads, or ether column 2 is operated to take overhead ethercontaining 0.5 vol. percent or less of alcohol, the ether stream mayby-pass ether Washer 7 and flow directly to the purification system vialine 24.

In the ether purification section the crude ether is admixed, ifnecessary, with additional quantities of ethanol introduced via line 13to bring the total ethanol content to at least 0.5 vol. percent andpreferably about 1%. The ether-ethanol mixture is then passed to mixer15 wherein it is contacted and thoroughly mixed with sodium plumbitesolution introduced via line 14. About 1 hour contact time is usuallysatisfactory.

After mixing, which may be by means of a centrifugal pump, agitator orother known-means, the mixtureds passed for settling to vessel 16,where, upon stratific'a tion of the layers, the sodium plumbite solutionmay be drawn oif via line 17 for recycle until the active purify ingagent is spent. I

The treated ether is passed via line 18 for finishing. It is passed todehydration column 19 where water is removed by condensing, cooling, anddecantation in condenser-accumulator 26. Water is discardedvia line 21.

The crude dehydrated ether containing possibly some high boilingimpurities is now passed to fractionator 23 where high boilingimpurities are taken as bottoms and high purity finished ether asoverhead. 7

Ihe purification steps which have been described with referenee'r'fiai'fily' "to 1 ditfiyl fl'ie'r are fiffilic'blto simple and mixeddialkyl etherscontaining from 4 to 6 carbon atoms per molecule. Also,though the invention has-Dbeen deseiibed in reonneetion with ethers:prepared bwabsorption mfi otefins ini zHeSmyit niay els'cibe'iemployi'edzini purifying fethers pnepar ed by other' m'ea'ns, suchasllay diiecti-hydrationzof olefins. ier thefetherpurifyingereagentpNafiHrnay bareplaced by other alkalis siich''a'sfiKOl-lfNazGitDs;iKaCosietb. w i a The process ofthesprese'ntsinventionimayfbei further illustrated: by thefollowingsspecificz-examples. .:In .the examples the: sodium :plumhitetieatifigragent WflSipIfipared Zby':saturating 11'"wt.spercent-:causticksolutiqnwith 155% -:lead'-oxide. This solittion;containingr ahout 3% sodium plumbite, was diluted with varyin'g amountsof' Water; in the examples; -the--strength of; the solution :u's'edis=expressedflas weight percent-sodium plumbite.

---By odorclass,reference is'had-to an arbitrary-scale for measuring andcomparing odorof {ethyl ether. The. odor of ethyl et-her -issoiintense'that little'foreign odors can;he=d etected until the-etherhas fairlywell' evaporated and foreign; odors -have'-become--eoncentrated. In the scale,class 3 designates an ether having nodetectable foreignpdor, and glass 12 an=etherhaving'strongly"objectionable odors. -The ascending numbers correspond toincreasingamounts of these objectionable odors.

Example' l In the laboratory experiments Below, -crude ether fromthedistillationsction 'was shaken with the plnmhite solution inase'patatoryTunnel. The"water layer was then I'eniovedandthe'ether"distilled. "Clude ether was treated withl0 volumepercent of thesolutions shown and then solution shown. The treated ether was thendistilled usratings of the various cuts. is shown. An asterisk indicatesthat 1% alcohol was added.

10% Cuts Blank Water 15% 46% 10% KOH KOH NaOH 6-8 V .a as

65% Sulfuric 2% Acid Plumblte a (DO alcohol) 10% NBHS 3 Black WhitePlumbite Example -Sodium=--pl=umbite has; been usedto --"sweetensour.gasolines, e."thoseecontaining small amountsof sulfur. That in; theease of -thepresent ;process "a :sweetening does -'-not occur is shownbythefollowing data wherein distilledusingse3oplates'and'refluxratios of1/1 'tdlO/l. the effectsof sodiumthypocmofltgi aqw lbkno n jfswgep i u V7 ening :agent is applied -tothe crude ether. ilnt t'his N6 l DEthel-101 added Crude example, the ether. is treated. with- 2.- -volume;percent 10f alkaline hypoch lori-te with and. without-added ethanol. 7 ggf 'w sodium Plumbite It will-be-notedthat'no improvement?took place.Treatment Blank Plugnb-Blank t and 3 a 4th Mb 40 'j V k "10% .Ou'ts:Blank"Na%(l,2N'Vl;t-0.%er((ie;1t Na v$lf2gzsgetcent lifiii ii ii ffi .5if; P ercent EIOH add d- Percent n'ron added odor; rg "NaOH -to'=Ether)NaOH toEther) -90%0verhead '8 6 6 3 13 3 3 5 t 1'1; nit-10 ns-1o s;10-s-10 8-10 'These re'sults' sho'w the marked improvement of-the $131111:6.2 3 S 3 ether'fo'dor when treated in accordance' with the process ofthe present invention. They further show the necessity of maintaining a'definite amount'of ethanolin the; ether. Example 5 The ethanol probablyacts-as a mutnal solvent, though the niutualsolvent effect doesnot-aloneaccount for'its necessity. Other?mutualsolvents, such asisopropanol, are =not=etfective.

Example 2 *In another set of laboratory runs, "the -'effect of 2%ethanol in the ether 'to 'be treated was determined.

f2 vol. percent No Eth- Ethanol Added anal 'Added Tratment nm- BlankTreated Treated bdorOlass; s 's a s i Here it is seen that noimprovement ataall was obtained on: treating "ethanol-free: ether with:10 volume;- percent sodium-plumbite in the absence of ethanol.

Example 3 Crudeether' was' treated' 1 0 volume percent of the i PreviousExamples 1' and 2Jhaveshown the necessityof maintaining alow-*molecularweight alcohol, and particularly ethanohinthe'treating'stage. Datahelow show that thisalcohol-preferablyismethyl'orethyl; 'isopropanol apparently is not effective. Primary :alcoholsare :preferr'ed 'fofthis-serviee.

' No Aleohol+i Plurnblte 0.2% "Santo merse" Plnmbite 57 ETo'-ir+Plumbite 1% 'IPOH+ Plumbite MeOH+ Blumblte Blank i Plumb ite presence ofa primary alcohol with a solution of an alkali plumbite, said alcoholand alkali plumbite being present in an amount sufficient tosubstantially free the ether from said foreign odors and thereafterdistilling said treated ether.

2. An improved process for purifying crude alkyl ether contaminated withforeign odor-imparting impurities which comprises contacting said etherwith an aqueous solution of sodium plumbite in the presence of a minoramount of an alcohol selected from the class of methanol and ethanol,said alcohol and sodium plumbite being present in an amount sufiicientto substantially free the ether from said foreign odors distilling saidtreated ether and recovering a purified ether product.

3. An improved process for purifying diethyl ether contaminated withforeign odor-imparting contaminants which comprises contacting saidether in a treating zone with an aqueous solution of sodium plumbite inthe further presence of from about 0.5 to about 10% by volume of ethylalcohol and distilling said treated ether.

4. The process of claim 3 wherein said alcohol is prescut to the extentof about 1-2% by volume of ether in said treating zone.

5. The process of claim 3 wherein said ether is treated with a 0.540%aqueous solution of sodium plumbite.

References Cited in the file of this patent UNITED STATES PATENTS INitardy Sept. 8,

1. AN IMPROVEMENT PROCESS FOR PURIFYING A CRUDE ALKYL ETHER CONTAMINATEDWITH FOREIGN ODOR-IMPARTING CONTAMINANTS WHICH COMPRISES CONTACTING SAIDETHER IN THE PRESENCE OF A PRIMATY ALCOHOL WITH A SOLUTION OF AN ALKALIPLUMBITE, SAID ALCOHOL AND ALKALI PLUMBITE BEING PRESENT IN AN AMOUNTSUFFICIENT TO SUBSTANTIALLY FREE THE ETHER FROM SAID FOREIGN ODORS ANDTHEREAFTER DISTILLING SAID TREATED ETHER.